1. Field of the Invention
The present invention relates to a keyboard with elevated keys, and in particular to a keyboard with keys that can be elevated sequentially.
2. Description of the Related Art
FIG. 1A is an exploded view of an elevated key of a conventional keyboard. In order to simplify the drawing, FIG. 1 only shows one elevated key of a conventional keyboard. In FIG. 1A, the elevated key of a keyboard for a notebook computer includes a key cap 11, a cap support 12, an elastic sheet 13, a circuit membrane assembly 14, a base sheet 15 and a guiding sheet 16.
The base sheet 15 is a metal sheet on which two seats 151 and a hook 152 are formed by punching and contacting.
The circuit membrane assembly 14 is disposed on the base sheet 15. It comprises the circuit of the keyboard and a plurality of holes 141 with respect to the seats 151 and the hook 152 of the base sheet 15.
The elastic sheet 13 has a sheet-like body, an elastic dome 131, a connecting portion 133 and holes 132. The connecting portions 133 connect the elastic dome 131 and the sheet-like body. Further, the elastic dome 131 has a plunger (not shown) inside to contact the circuit membrane assembly 14 and conduct the circuit on thereto.
The guiding sheet 16 is disposed on the elastic sheet 13 and can be moved horizontally. It has two L-shaped hooks 161 and a hole 163 with respect to the elastic dome 131 of the elastic sheet 13 and the seats 151 and the hook 152 on the base sheet 15.
The cap support 12 has a first linking bracket 121 and a second linking bracket 122 which hinged together and as a scissors-type support mechanism. Furthermore, the first linking bracket 121 has shaft rods 1212, 1213 formed on both sides thereon. The second linking bracket 122 has shaft rods 1221 formed on both sides thereon.
FIG. 1B is a schematic back view of a key cap of the elevated key in FIG. 1A. In FIG. 1B, the key cap 11 has hooks 111 and holding portions 112 on its bottom surface.
FIG. 1C is a schematic view of the elevated key in FIG. 1A with the key cap removed. In FIGS. 1A˜1C, while assembling the conventional elevated key, the circuit membrane assembly 14, the elastic sheet 13 and the guiding sheet 16 are put on the base sheet 15. The seats 151 and the hook 152 of the base sheet 15 protrude through the holes 141 of the circuit membrane assembly 14, the holes 132 of the elastic sheet 13 and the hole 163 of the guiding sheet 16. The key cap 11 is mounted on the base sheet 15 via the cap support 12. The shaft rods 1212 are inserted into the seats 151 so that the first linking bracket 121 is rotatable with respect to the base sheet 15. The narrow portion 1223 of the second linking bracket 122 is hooked by the hook 152 of the base sheet 15 so that the second linking bracket 122 is also rotatable with respect to the base sheet 15. The hooks 111 hold the shaft rods 1213 of the first linking bracket 121, and the holding portions 112, hold the shaft rod 1222 of the second linking bracket 122. Furthermore, in FIG. 1C, the L-shaped hooks 161 selectively press both arms of the first linking bracket 121.
In operation, the user pushes down the key cap 11 and compresses the elastic dome 131. Then, the elastic dome 131 deformed and pushes the circuit membrane assembly 14 so that an electric conduction therein is induced and sends out a corresponding signal.
FIG. 2A and FIG. 2B are cross sections of the elevated key according to the FIG. 1A when the guiding sheet is in a first position and in a second position correspondingly. In FIG. 2A, when the guiding sheet 16 is in the first position, the hooks 161 contact both arms of the first linking bracket 121, and the key cap 11 is in the original typing position. In FIG. 2B, when the guiding sheet 16 is in the second position, the hooks 161 presses both arms of the first linking bracket 121. The scissors-type support structure approaches the base sheet 15, such that the key cap 11 descends to the depressed position. Furthermore, when the guiding sheet 16 returns to the original position in FIG. 2A from the depressed position, the hooks 161 release the first linking bracket 121, or the scissors-type linking mechanism. The elastic dome (not shown) provides an elastic force to elevate the key cap 11.
The conventional keyboard for a notebook computer has at least 100 keys. The friction force between the guiding sheet 16 and the arms of the first linking bracket 121 is very large when moving the guiding sheet 16 to depress all of the keys 11. Thus, it needs a thick guiding sheet to provide a large horizontal force to overcome the friction and contact all of the keys at the same time, but the thick guiding sheet increases the profile weight of the notebook computer.